1. Field of the Invention
The present invention relates to a developer storage container such as a development device, a toner container, and a toner cartridge incorporated in an image forming apparatus such as a copier, a facsimile, and a printer. In particular, the present invention relates to a method for preventing developer leakage from inside a container.
2. Description of Related Art
In image forming apparatuses such as copiers, printers, and facsimiles using electrophotography method, powder developers are mainly used, and the following image forming process is typically performed therein; an electrostatic latent image formed on an image carrier such as a photoconductor drum by using a development device is visualized, the visualized image is transferred onto a recording medium, and then fixing is performed.
A casing of such a development device is typically composed of: a housing (container main body) that has an agitation-conveyance member, a developer carrier, and the like arranged therein and in which a developer is stored; and a cover (lid body) that closes an opening of the container main body. An elastic member made of sponge, rubber, or the like is attached to a fitting surface of either the housing or the cover, and the elastic member is compressed between the fitting surfaces when the housing and the cover are fitted together, whereby air-tightness of the development device is secured.
In the above structure, however, the part that comes in contact with the top end part of the elastic member is formed of a resin of which the housing and the cover are formed. As a result, particularly in a case in which a housing and a cover are fitted to each other by a snap fitting, vibration or shock applied from outside is liable to cause a gap or displacement between the elastic member and the resin member that is in contact with the elastic member, and this may invite developer leakage.
To cope with this inconvenience, there have been proposed methods of preventing powder from leaking out of a powder charge container that is divided into at least two parts. For example, JP-A-2000-238864 discloses a powder charge container in which elastic particles are adhered to fitting surfaces of a plurality of parts of a container, and the fitting surfaces are detachably fitted to each other by being pressed against each other.
In a case of fitting by using a snap fitting, predetermined clearance (extra space) is provided in a fitting part to improve the workability in fitting and detaching a cover to and from a housing. Thus, it is necessary to adjust the cushioning characteristic and the thickness of an elastic member attached to the fitting part to be within a preferable range. For example, too weak cushioning characteristic (elasticity) or too small thickness of the elastic member reduces adaptability of the elastic member with respect to displacement occurring at the fitting part. As a result, a gap is liable to be formed. If the elastic member is too thick, its elasticity is liable to cause deformation of a resin member.
However, with the method disclosed in JP-A-2000-238864, in which only one layer of elastic particles is adhered to each of the fitting surfaces, the thickness of the elastic layer needs to be adjusted by using elastic particles having a different diameter or by changing a number of times of repetition of adhesive layer application and elastic-particle attachment to the adhesive layer. This disadvantageously lowers manufacturing efficiency. In addition, JP-A-2000-238864 describes, as a method of fitting the container parts to each other by applying pressure, only a method of fitting them to each other by using a screw member; no description is given with respect to the above mentioned relationship between a snap fitting and the cushioning characteristic and the thickness of an elastic member.
Incidentally, although the above description deals with developer leakage from the casing of a development device, the casing of a toner container or of a toner cartridge supplying a developer (toner) to a development device suffers from the same inconvenience.